Scripts with sound path - Imported audio not working with Save Game as Runtime
Referring to a file in a python script doesn't tell blender that it is using an external file, so it isn't included when packing external files.

You can add a sound strip to the Video Sequence Editor or you could add a speaker in the 3D scene and open the sound file with that. Both of these methods allow blender to pack the audio file into the blend and I expect that both will be included when exporting to the game engine runtime.

An even better approach would be to use a sound actuator and open the sound file with that, which allows it to be packed. You can then use the actuator to play the sound or access other properties with a python script, you can also use sensors to play the sound without the script.

cont = bge.logic.getCurrentController()
actu = cont.actuators['Sound']
cont.activate(actu)